BirdAnalyst
Species · South Carolina · BBS 2026 Release · 1966–2025

Brown-headed Cowbird Population Trend in South Carolina

All statesGeneralists

Brown-headed Cowbird in South Carolina has surged: up 557% on the route-weighted index since 1968.

+557%Since 1968TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
50Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Brown-headed Cowbird Trends in South CarolinaNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc increasecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Brown-headed Cowbird has surged in South Carolina: up 556% on the route-weighted index since 1968.

Brown-headed Cowbird Population Forecast in South Carolina

If the recent trend holds, Brown-headed Cowbird in South Carolina is projected to rise about 11% by 2030 — from 5.8 in 2025 to a central estimate of 6.4 (95% range 3.3–9.5). A 5-year backtest shows a typical error of ±27.5%, with 100% of held-out values landing inside the 95% band.

+11%Change by 2030TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
6.4Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
3.3–9.595% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±27.5%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Brown-headed Cowbird in South Carolina is projected to rise about 11% by 2030 — from 5.8 in 2025 to a central estimate of 6.4 (95% range 3.3–9.5). A 5-year backtest shows a typical error of ±27.5%, with 100% of held-out values landing inside the 95% band.19662030
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20266.23.19.3
20276.23.19.3
20286.33.29.4
20296.33.29.4
20306.43.39.5

Brown-headed Cowbird Survey Routes in South Carolina

Routes recording Brown-headed Cowbird in South Carolina.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Ward1920252017
Holly Hill1720251972
Coward1620251974
Little Mtn1519881977
Pinewood1520191998
Bennettsville1420171998
Kingstree1120102010
Nixville1120251998
Rome1020251974
New Ellenton1020252010
Red Bluff1020251996
Blacksburg920111998
Dillon820211973
Pendleton819761966
Lowrys820252017
Kiawah Island820251998
Chesnee820151992
Green Sea720252010
Carvers Bay720121998
Owings 2720252005
Hardeeville620251968
Nixonville619951987
Prosperity620241992
New Holland520251970
Sandhills420251995

Brown-headed Cowbird Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.